I have a C++/CLI library that I would like to use in a Silverlight application. It is supposed to be possible to write code for Silverlight in any .NET language, but so far I've only worked out how to compile C#. Silverlight does not seem to be able to use DLLs compiled for .NET.
I'm using Visual Studio 2010 and Silverlight 4. The only new projects available for Silverlight are C# projects. Porting the code to C# is not a practical option.
How do I compile C++/CLI code for Silverlight?
I think I may have gotten a VS2010 C++/CLI class library project to build with references to (only) Silverlight assemblies.
Ok, it is possible. But it is not nice.
First, you must convince the C++ compiler to NOT load the .NET Framework, using an undocumented compiler switch. But that's not the worst part.
/clr:safe
/d1clr:nomscorlib /FU"C:\Program Files (x86)\Microsoft Silverlight\4.0.50917.0\mscorlib.dll"
Now, save the project and exit Visual Studio. Open the .vcxproj in a text editor, and change the framework version setting. You want it to be the same as a C# Silverlight project:
<TargetFrameworkIdentifier>Silverlight</TargetFrameworkIdentifier>
<TargetFrameworkVersion>v4.0</TargetFrameworkVersion>
<SilverlightVersion>$(TargetFrameworkVersion)</SilverlightVersion>
Now, reopen Visual Studio, and build the project. You'll get an error because the compiler auto-generated a file with #using<mscorlib>
and the search path finds the .NET Framework version first.
Silverlight,Version=v4.0.AssemblyAttributes.cpp(1): fatal error C1197: cannot reference 'c:\windows\microsoft.net\framework\v4.0.30319\mscorlib.dll' as the program has already referenced 'c:\program files (x86)\microsoft silverlight\4.0.50917.0\mscorlib.dll'
Double-click the error to open the auto-generated file. Replace the path-less reference with e.g. (here's where you put your references, not in the project properties)
#using <c:\program files (x86)\microsoft silverlight\4.0.50917.0\mscorlib.dll>
#using <c:\program files (x86)\microsoft silverlight\4.0.50917.0\System.dll>
#using <c:\program files (x86)\microsoft silverlight\4.0.50917.0\System.Core.dll>
Luckily, the compiler leaves your changes in-place. So you should be good as long as no one cleans your temp directory.
Then, you need to go add the DLL created by the C++/CLI project to your Silverlight application. Note that you can't set up a project reference, because VS2010 still isn't convinced that the C++/CLI is a Silverlight project. So you'll have to browse and add the reference as an assembly file. (And it won't automatically switch between Debug and Release to match the Silverlight application).
I got it to run an empty Silverlight application in Debug mode and stop at a breakpoint in the middle of C++/CLI code. Also the C++/CLI code successfully returned a value to C# and the local variable in C# received the correct value. So I guess it's working.
I went through a bunch more steps trying to make this work, but I don't think they affected the outcome. If you run into errors, though, let me know and I'll try to figure out what I omitted from this answer.
Ben Voigt, thanks for this, it worked for me too.
Also, if your C++ code does anything that is specific to the C++ language (i.e. not entirely IL portable) like using stack semantics for an array, you'll get the following error:
could not find assembly 'Microsoft.VisualC.dll' etc.
If you recompile with the full .NET Framework and then dump the IL code, you'll find references to "''.$ArrayType$$$BY06$$CB_W modopt" or something similar. This tells you where to change the code.
I found that after I installed the Silverlight SDK and it got added to "\Program Files(x86)\Reference Assemblies" I did not have to go through all of Ben Voigt's steps, just changing the project file was enough.
Another note, you can also use:
<TargetFrameworkProfile>WindowsPhone71</TargetFrameworkProfile>
if you want to target Windows Phone (install the SDK first).
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